A reactor pressure vessel (RPV) of a boiling water reactor (BWR) typically has a generally cylindrical shape and is closed at both ends, e.g., by a bottom head and a removable top head. A core shroud, or shroud, typically surrounds the core and is supported by a shroud support structure.
Boiling water reactors have numerous piping systems, and such piping systems are utilized, for example, to transport water throughout the RPV. For example, core spray piping is used to deliver water from outside the RPV to core spray spargers inside the RPV. The core spray piping and spargers deliver water flow to the reactor core.
Stress corrosion cracking (SCC) is a known phenomenon occurring in reactor components, such as structural members, piping, fasteners, and welds, exposed to high temperature water. The reactor components are subject to a variety of stresses associated with, for example, differences in thermal expansion, the operating pressure needed for the containment of the reactor cooling water, and other sources such as residual stresses from welding, cold working and other inhomogeneous metal treatments. In addition, water chemistry, welding, heat treatment and radiation can increase the susceptibility of metal in a component to SCC.
Reactor internal piping, such as T-boxes and core spray line risers, occasionally require replacement as a result of SCC. Replacing the core spray piping often requires removing and replacing the core spray line riser. The core spray line attachment to the shroud, however, typically is installed during original reactor construction and is difficult to access. In addition, replacing the core spray line riser, particularly the attachment to the shroud, is complicated by the limited available working space.
The core spray line riser includes a lower elbow secured to a core spray sparger T-box. There are a number of welds between the lower elbow and T-box, and the integrity of these welds must be maintained to ensure proper operation of the core spray piping. As explained above, it is difficult to access these welds.
It would be desirable to provide an apparatus which facilitates providing additional support for the welds between the core spray sparger T-box and the lower weld of the lower elbow of the core spray line riser. It would also be desirable to provide such apparatus which is easy to assemble and install in a limited working space.